Ive used BMC CDA on the 1.2 16v, collecting ar from above the radiator - for that youll need to remove that plastic on the top of the rad. But I live in Portugal and it doesnt rain that much, so be careful because theres always the possibility of water going in!
A dyno run reported 2bhp and 3NM gain, but since the engine gets pressured air from the front, at speeds above 130kmh (~80mph) the engine revs faster, and top speed benefits from it too!
From all the things Ive tried to improve this engines performance, a good induction kit is by far the best that money can buy.
BTW, fuel consumption also drops a bit!
On a more personal note, I think you guys should spend your posts trying to help people, not waging wars. My .02€
*edit* Forgot to mention: theres no way youll gain performance by reworking the original box, much less by simply changing the filter, the way to do it its to get rid of the whole thing.